FindFiles exits and returns no files when it can't open a directory

This program

```
package main

import (
	"log"
	"os"

	".com/bitfield/script"
)

func main() {
	h, err := os.UserHomeDir()
	if err != nil {
		log.Fatal(err)
	}
	_, err = script.FindFiles(h).Stdout()
	if err != nil {
		log.Fatal(err)
	}
}
```

yields:

```
$ go build
$ ./script
2022/03/12 11:51:51 open /Users/user/.Trash: operation not permitted
```

I expected behavior similar to `find $HOME -type f`, i.e. to return files from directories it can open. 

Description